This invention relates in general to gyroscopes and more specifically to ring laser gyroscopes.
Navigational systems represent an important use of gyroscopes since it is important to know and/or maintain a specific orientation of a vehicle or movable device relative to another location or object. A gyroscope outputs information related its change in orientation and hence can determine the orientation of the vehicle to which it is mounted. This output information can be processed and displayed to provide a measurement of the orientation of the vehicle and can also be used as a feedback signal coupled to a propulsion system to maintain a specified orientation of the vehicle.
Conventional gyroscopes with a spinning wheel make use of the effect of precession in which the spinning wheel maintains its orientation relative to the plane in which the wheel spends. Although spinning wheel gyroscopes have been effective, such gyroscopes have limitations in accuracy and durability due to friction and mechanical aspects associated with the spinning wheel.
The ring laser gyroscope represents an improvement over the spinning wheel gyroscope by eliminating the need for moving parts. The Sagnac effect is a relativistic effect related to the rotation of a closed optical path. The Sagnac effect in a ring laser results in a frequency difference between counter rotating laser beams (modes) when the ring is rotated such frequency difference being proportional to the angular rate about an axis perpendicular to the plane of the beam path. A conventional ring laser gyroscope uses a series of mirrors to reflect two free-space laser beams in opposite directions around a “ring”. The ring consists of a triangle, rectangle, or other closed multiple-sided geometric configuration in which mirrors are disposed at the corners to reflect the laser beams along the adjacent straight legs in the configuration. The two laser beams create a virtual interference pattern or standing wave around the ring which remains stationary in inertial space. The movement of a ring laser gyroscope about the plane of the ring causes a shift of the position of the body of the gyroscope relative to the standing wave depending on the direction of the movement of the gyroscope. A detector coupled to the ring measures the position of the detector/ring relative to the standing wave and provides an output signal related to the change in orientation of the ring.
Extremely high-quality mirrors are required for conventional ring laser gyroscopes and must be made to exacting standards of flatness, high reflectivity, and low dispersion. Producing the mirrors to such exacting standards results in high manufacturing costs that must be reflected in the total cost of the gyroscope. Thus, there exists a need for an improved gyroscope that can substantially overcome the difficulties and costs associated with requiring multiple mirrors.